Preincubation of human and porcine thyroid membranes in high concentrations of ammonium sulfate resulted in an increase in high affinity TSH receptors without change in low affinity receptors. Various forms of intracellular and extracellular TSH differing in carbohydrate content displayed different receptor-binding and adenylate cyclase activities. Lymphapheresis caused a major decrease in serum thyroid-binding immunoglobulins in 2 patients with Graves' Disease.